Physics and Chemistry of Fracture and Failure Prevention

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Assurance of reliability of materials and structures with synergistic effects of combined environments by mechanical, chemical, radiation and high temperature conditions is extremely important for prevention of failure and accidents. In general, failure accidents are initiated by local damage and its extension by aging. Therefore, in order to prevent these failures, detection and evaluation of the degradation at an early stage is essential. Especially, technology for 21^<st> century will go towards more precise, higher speed, higher efficiency and higher temperature and pressure and consequently, surrounding environments which materials and structures will face to can be severer than before more.The objective of this research program is to conduct a comprehensive research on mechanics and mechanisms of fracture and to construct a failure prevention system.It has been well recognized that the macroscopic approach such as Fracture Mechanics has been successfully used for structural integ … More rity and safety assessment in purely mechanical loading condition but not in environmental condition where physical and chemical reactions at crack tip plays a crucial role in fracture. Therefore, a local approach is mandatory for mechanistic understanding of this complicated fracture from a viewpoint of physics and chemistry of fracture. Measurements of local information such as local characteristics of materials, local environment such as local water chemistry at crack tip, for examples, are essential for the local approach. In the same way, local crack tip strain and tiny defects are also of importance for the local approach. These local measurements are in the order of a few nanometer to several hundreds micrometer and several tens nano-liter to a few micro-liter. Especially, an emphasis has been placed to carry out the research on crack initiation and early stage of propagation based upon local parameters obtained by a fusion of various local information, which govern the most of the life time of the components.In this program, following research areas have been covered as, (I)mechanistic understanding of physics and chemistry of fracture, (II)-1 methodology development for local measurements of materials chemistry, (II)-2 methodology development for local measurements of crack tip water chemistry, (II)-3 methodology development for local measurements of crack tip mechanics, (II)-4 methodology development for local measurements of defects (III) construction of a prediction system of failure based upon a fusion these local information.The program has been carried out by the research group shown below who have been made a significant contribution internationally on the research areas of physic and chemistry of fracture, grain boundary engineering, raser ultrasonic microscope, intelligent instrumentations, fracture in complex systems, damage evaluation and so on. After this program, this activity has been reinforced by initiating a new research institute, Fracture and Reliability Research Institute as a new extension of former Fracture Research Institute. The Institute maintains the facilities, spaces and international research network Less